<p><ahref="http://paulirish.com/">Paul Irish</a> was so kind as to pass on a few bugs that have surfaced.</p>

<ul>

<li>In recent versions of Chromium, mixing <code>optimizeLegibility</code> and <code>font-variant: small-caps</code> will <ahref="http://code.google.com/p/chromium/issues/detail?id=51973">cause the small-caps to not render</a>.</li>

<li>Irritatingly, it also causes text to <ahref="http://developer.palm.com/distribution/viewtopic.php?sid=0d2709e0a7fd4fec26c9278d0129d9d8&lastaction=login&f=55&t=8445">disappear completely on webOS</a>.</li>

<li><ahref="http://make-believe.org">Joseph Pearson</a> also points out that on slower machines (such as mobile devices) it can negatively impact page load when applied to large blocks of text.</li>

<li>In Safari 5, when using a measurement type of <code>ex</code> on the <code>margin</code>, <code>padding</code>, <code>border-width</code> or <code>outline-width</code> properties causes the browser to crash. See his demo page here: (warning: this will crash safari, obviously) <ahref="http://quorning.net/safari_crash.htm">http://quorning.net/safari_crash.htm</a></li>

A bit offtopic, but: what's the point of writing background color of body in this manner? — background: rgba(30, 10, 0, 0.05) — this is just #F4F3F3 (faster for rengering, I guess) and you actually relying on default background color in particular browser, which can be changed:

Why I'm asking? It's seriously harms rendering in Opera browser. I know, this is problem of Opera, but I'm just curious.

I filed a bug report to Apple yesterday, telling that Safari crashes when I use text-rendering: optimizeLegibility together with either margin, padding, border-width or outline-width measured in ex. It works fine with em, px, in, % etc., though. I’ve put together an example page at http://quorning.net/safari_crash.htm

I've spent nearly a day trying to work out why Android 2.3's Browser (via browserstack) was crashing out completely on a fairly simple page. I looks to be suffering the same ex-units bug as the Safari versions discussed already. Perhaps an old Webkit issue rather than just Safari? It seems resolved in newer Androids and iOS versions, but it's worth noting if you're legacy device testing.